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• due to the fines and sediments that will settle out of the mine wat~r and drop to the pond floor and sides. This is demonstrated by the existing lays on the pond bottom due to prior operations. Lab tests on this materia demonstrated that it is a low plasticity clay (CL) which is typical y a very suitable soil For minimizing seepage or leakage. In addition to the berm construction (discussed in the next section being typical of that normally required for water storage dams, these pon s are in agreement with the Hest Management Practices (BHP) listed in the pr amble to the Categorical Standard For Placer Gold Hine Operations (53 FR 187 5). Berms shall be constructed in a manner such that they are reasonably expe ted to reject the passage of water. "This may be achieved by utilizing on ite materials in a manner that the fine sealing materials, such as clay , are mixed in the berms with coarser materials." This approach has been taken both in the berms as well as sealing the bottoms of the impoundments. L boratory tests demonstrated that the fines are indeed appropriate for use, a d several previous statements have been made that the Eines and onsite materi is will be used to seal the impoundments. EHBAHRHEHT STABILITY The June 6 submittal described the type of soils used to construct the berm and the fact that the 3:1 slopes were conservatively chosen accordi~{Ifg to Desien of Small Dams, a Bureau of Reclamation publication that is a standard • reference text that is used by virtually all knowledgeable dam desi Hers. The Since the tiLRD staff still seems to be uncertain regarding the stability of the berm a computer was utilized to run stability analyses of the b rm design. A homogeneous embankment was assumed, with a phreatic surface assum d to be from the normal operating water level three Eeet below the crest to the one third height of the downstream slope of the dam. This is a standar conservative assumption of long term, steady-state conditions of a omogeneous embankment. The basic parameters utilized in the computer analyses were 3:1 side slopes, 15 Eoot wide crest, the phreatic surface already menti ned, dry soils density of 125 pounds per cubic foot in keeping with onsite s ils testing results, a saturated unit weight of 134 pounds per cubic Eo t, friction angle of 35°, and cohesion of from 0 to 500 pounds per squ re foot (pFs). Stability analyses were run for various levels of cohesion. The most conservative factor of safety obtained was with 0 pfs cohesion. Th resultant factor of safety was 3.09, which is far in excess of the 1.5 normal y required conservativeness of this approach is demonstrated in a discussion o Best Management Practices (53 FR 18785) which states, "The side slope of berms should not be, greater than the natural angle of repose of the materials used in the berms or a slope of 2:1 whichever is lower." The berms here have been designed at a slope of 3:1 which is more conservative than the 2:1 lope discussed in the Best Management Practices. It is far less steep t an the natural angle of repose of the material. We therefore feel that th information provided in the June 8 report clearly demonstrated that conservative assumptions were used in the berm design and construction. • by the State Engineer's Office when evaluating Laboratory tests of the existing soils suggest cohesion value is approximately 500 pounds per factor of safety with the embankment including again is far in excess of the State Engineer's -3- dams of this nature. that a more appropri to square foot. The as ociated this parameter is 7. , which Office requirements. We have